Loyalty (or bonus) points program can help merchants encourage their customers to place repeat orders.
osCommerce v4 is coming with Loyalty points program feature (likely to be an add-on).
Every product can have two points values - the amount it "costs" in points, and the amount it can give the customer if the customer buys it.
Value of points the customer can gain by buying this or that product can be displayed on product info pages and product listings too.
During the Checkout, existing customers can see their balance in points and choose to redeem certain amount of points, using loyalty points as a payment method.
Points can be checked, and edited in the back end for each customer.
Further developments may include some more advanced promotional mechanisms that will involve loyalty points.